The court said that the 21-year-old from Wyoming, Ohio had committed a crime "pursuant to the U.S. government's hostile policy toward (the North), in a bid to impair the unity of its people after entering it as a tourist."

Before the trial, Warmbier tearfully told reporters that he had tried to steal a propaganda banner for a friend of his mother's, who wanted it as a trophy to hang it in her church in Wyoming.

He said he was offered a used car worth $10,000 if he could get the banner, the AP reported. He said that he was told that if he was detained and didn't return, his mother would receive a charitable donation of $200,000.

He went ahead with the plan because his family was struggling financially, he said.

Warmbier added that he also took the banner partly at the urging of a secretive student group at his university, an organization called the ‘Z Society.’

“I eagerly wanted to join the Z Society,” he said at the press conference.

The society is said to be a secretive by philanthropic group. One member was quoted as saying the organization never had any contact with Warmbier.

He was arrested at the airport before a flight to China on January 2. He had been traveling with the China-based company Young Pioneer Tours, the agency confirmed in a statement. The State Department warns against travel to North Korea, although it is legal.

At the time, North Korea said he had committed an anti-state crime with "the tacit connivance of the U.S. government and under its manipulation," although it is not clear how the U.S. government was allegedly connected to the student's actions.

"When I heard, I was just shocked and immediately I was just so sad," the friend said.

"He comes from a small town within Cincinnati and I'm sure everyone over there is heartbroken. There couldn't be a worse person for this situation to happen to. I can't even wrap my head around this right now. It's surreal."